Compact optical transceivers including thermal distributing and electromagnetic shielding systems and methods thereof

ABSTRACT

An optical transceiver includes structures that define an electrical connector port for allowing connection of an electrical connector to an optical subassembly of the transceiver, and structures that define a vent surrounding at least portions of the connector port, whereby the vent allows bidirectional passage of air therethrough. Included in the transceiver are structures that define electromagnetic interference shielding and selectively transfer heat of heat generating electronic components by conduction to a transceiver housing. Methods of cooling the transceiver by ventilation and internal heat conduction are present.

REFERENCE TO PARENT APPLICATION

This patent application is a divisional of the co-pending patentapplication “COMPACT OPTICAL TRANSCEIVERS INCLUDING THERMAL DISTRIBUTINGAND ELECTROMAGNETIC SHIELDING SYSTEMS AND METHODS THEREOF”, Ser. No.09/809,699 filed by Anderl et al. on Mar. 15, 2001, which isincorporated herein by reference.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is related to the following commonly-assignedand copending U.S. Patent Applications: U.S. Ser. No. 09/809,650entitled: AN OPTICAL FIBER COUPLER AND AN OPTICAL FIBER COUPLERINCORPORATED WITHIN A TRANSCEIVER MODULE; U.S. Ser. No. 09/809,531entitled: TECHNIQUE AND APPARATUS FOR COMPENSATING FOR VARIABLE LENGTHSOF TERMINATED OPTICAL FIBERS IN CONFINED SPACES; U.S. Ser. No.09/809,127 entitled: HIGH FREQUENCY MATCHING METHOD AND SILICON OPTICALBENCH EMPLOYING HIGH FREQUENCY MATCHING NETWORKS; all filed concurrentlyherewith and all incorporated herein as a part hereof.

BACKGROUND OF THE INVENTION

The present invention relates generally to a laser-based datacommunication interconnect apparatus for effecting optical data transferand, more particularly, to compact optical transceiver apparatus andmethods having improved thermal distributing and electromagneticinterference shielding features.

Optical transceiver modules are known in the data transmission field foreffecting bidirectional data transmission, whereby electrical signalsare converted to optical signals and vice versa. In operation, atransmitter unit of the module functions to convert incoming electricalsignals to corresponding optical signals. Conversely, incoming opticalsignals are converted by the module's receiving unit into correspondingelectrical data signals. These modules are typically mounted on acircuit host card that is normally associated with a host computer,input/output device, switch, or other peripheral device.

In general, space saving concerns are important to end users desiring touse such modules in order to satisfy established or emerging standardsas to a size or form factor. It will thus be appreciated that there is acommercial desire for relatively small and compact modules; especiallythose that are

adapted to be integrated into a wide range of existing and evolvingnetworking systems.

Not only are compactness concerns important for module design, but soare thermal management issues. This is because transceiver modules, inoperation, tend to generate relatively significant amounts of heat. Infact, as data transfer rates increase, for example in the multi-gigabitrange, so does the heat generated thereby owing to the higher amounts ofpower required. It will be appreciated, therefore, that the higher powerneeds and the desire for module compactness tend to increase the amountof excessive heat generated within a module having reduced space for itscomponents.

Not only do the smaller confines of a reduced sized module impactnegatively on overall thermal management issues in a general sense, butsuch compactness places some of the module's components that operate atrelatively high temperatures even closer to components that must operateat cooler temperatures, for optimal performance reasons, therebyadversely affecting the performance of the latter. For instance, inorder to maintain high performance reliability for a module's laserdiode, it should be kept relatively cooler than its associated driver;the latter of which tends to operate at much higher temperature ranges.Accordingly, significant and opposing design constraints are imposed onthe manufacture and reliable operation of such transceivers consideringthe countervailing demands for more powerful transceiver components andend user demands for module compactness satisfying industry standards.

Many known transceiver modules when mounted to an opening of a datasystem bulkhead tend to block the passage of cooling air therethrough.This blockage is, in part, necessitated by the desire of shieldingagainst excessive electromagnetic interference emissions emanating fromsuch opening. The blockage creates, however, a tendency for the interiorspace of the data system which houses the module to overheat, therebylessening the effectiveness of a module's internal cooling approach.Such blockages additionally place heating burdens on the data systemitself. This is especially troublesome to end users when they desiremore powerful transceiver modules because existing data systems may notbe able to effectively cool the additional heat being added thereto.

As a result, emphasis is being placed on the utilization of heat sinksand other means for managing heat issues arising from transceiver use.Known attempts at addressing the heating problems in transceivers ofthis type include those described in commonly-assigned U.S. Pat. No.5,757,998; issued to R. Johnson et el. This patent describes an opticaltransceiver having a cover and several components of the module servingas heat sinks. Also, insofar as electromagnetic interference isconcerned, known attempts at addressing the need for a low cost andreliable approach for the reduction of electromagnetic interferenceemissions when mounting a transceiver to a wall opening include thosedescribed in commonly-assigned U.S. Pat. No. 6,085,006; issued to D.Gaio et al. This patent describes an optical transceiver having anexternal electromagnetic interference shield that slides over a moduleend portion that encloses an optical fiber connection assembly. Theshielded end portion is retained in an opening of an associated datasystem for allowing connectors to be connected thereto.

While the known approaches have been successful concerning controllingthermal and electromagnetic interference issues, there is, nevertheless,a continuing desire to improve upon the control of such issueseffectively. For without improvements regarding effective thermal andelectromagnetic interference emission control management; especially ina compact and cost-effective manner, the ability of such transceivers tomaintain reliable optimal performance characteristics in a commerciallyviable manner will continue to be limited.

SUMMARY OF THE INVENTION

It is, therefore, a principal aspect of the present invention tocontinue to improve upon the thermal management control problems thatarise in optical transceivers.

It is, therefore, another principal aspect of the present invention tocontinue to improve upon the electromagnetic interference issues thatarise in optical transceivers.

It is another aspect of the present invention to continue to improve thethermal and electromagnetic interference management of a data transfersystem that uses an optical transceiver.

It is another aspect of the present invention to continue to improveupon thermal management control problems through effective convectivecooling of the heat generating components.

It is another aspect of the present invention to continue to improveupon thermal management control problems through effective and selectivecooling of the heat generating components.

It is yet another aspect of the present invention to provide a method ofcooling an optical transceiver that is mountable to an opening in a wallportion while providing the necessary electromagnetic interferenceshielding.

It is yet another aspect of the present invention to provide thermal andelectromagnetic interference mechanisms that effectively integrateelectromagnetic interference and thermal control solutions.

It is another aspect of the present invention to provide thermal andelectromagnetic interference mechanisms that achieve the foregoingaspects in a compact packaging arrangement.

It is yet another aspect of the invention to provide a heat sink portionexternal to a wall opening operating at temperature lower than heat sinkportions mounted within the wall opening.

It is still another aspect of the invention to use external heat sinkportions for cooling of an optical subassembly including its laserdevice.

It is yet another aspect of the present invention to achieve theforegoing aspects in a simple, reliable and low-cost manner.

In regard to achieving the foregoing aspects and further in regard toimproving over the prior art especially in connection with the issuesraised above, the present invention makes provisions for a method ofcooling an optical transceiver that is mountable in a wall opening. Themethod comprises the steps of: providing an optical transceiver havingat least one end portion that is insertable within the wall opening;and, ventilating ambient air over a major surface portion of the opticaltransceiver by mounting the one end portion to the wall opening so thatat least one vent is formed within the confines of the wall openingwhich allows air to pass therethrough and over the major surface portionof the optical transceiver. In addition, such a method comprises thestep of: shielding the optical transceiver, the vent, and the wallopening from electromagnetic interference.

Further consistent with achieving the foregoing aspects and improving onthe prior art the present invention makes provisions for a opticaltransceiver comprising: a housing assembly including a carrier memberand a heat sink cover member coupled to a portion of the carrier memberto define at least a portion of an enclosure therewith; an opticalsubassembly including an electro-optical transmitter unit positionedwithin the enclosure; a retainer assembly mounted on a first end portionof the carrier member and enclosing portions of the optical subassembly;the retainer assembly including a first set of structures which, incombination, with the carrier member define at least one electricalconnector port for allowing connection of an electrical connector to theoptical subassembly, the retainer assembly including a second set ofstructures which, in combination, with the carrier member define atleast one vent surrounding portions of the connector port, wherein thevent allows bidirectional passage of air therethrough, such that air caneasily pass generally over a substantial surface portion of the housingassembly; and, an electromagnetic interference assembly connected to atleast peripheral portions of the second set of structures and at leastperipheral portions of the first end portion for releasably coupling theoptical transceiver to an opening of a wall.

In an illustrated embodiment, the electromagnetic interference assemblyincludes a frame having a plurality of spaced apart and flexiblyresilient retaining tabs extending therefrom. The tabs allow the opticaltransceiver to be inserted into the wall opening and be releasablyretained thereby. The electromagnetic interference assembly is made ofan electrically conductive material which reduces electromagneticinterference emissions of the optical transceiver. The screen assemblyis coupled to the optical transceiver so as to be positioned adjacent toand in covering relationship to at least a portion of the vent. Thescreen assembly has a plurality of screen openings for allowing passageof air therethrough and reducing emission of electromagneticinterference.

Further consistent with achieving the foregoing aspects and improving onthe prior art the present invention makes provisions for an opticaltransceiver comprising: a housing assembly including a carrier memberand a heat sink cover member joined together to define a portion of anenclosure therebetween; an optical subassembly within said enclosure,the optical subassembly comprises an electro-optical transmitter unitincluding a first electronic device which operates at a firsttemperature range and a second electronic device which operates at asecond temperature range that is higher than the first temperaturerange. The first electronic device is thermally coupled to an internalsurface of the carrier member so as to transfer heat thereof byconduction to the carrier member. The second electronic device ismounted on a substrate located within the enclosure which substrate isnot in direct thermal contact with the carrier member. A thermallyconductive unit thermally couples the second electronic device to aninternal wall of the heat sink cover member in a manner so as totransfer heat by conduction from the second electronic device to theheat sink cover member and away from the first electronic device,whereby the first electronic device is maintained cooler than the secondelectronic device.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, reference isnow made to the following detailed description of a preferred embodimentof the present invention illustrated in the accompanying drawings inwhich:

FIG. 1 is a perspective view, with portions broken away, of an opticaltransceiver module made according to the present invention being mountedon a host circuit card of a data transfer system;

FIG. 2 is a perspective view of the optical transceiver module asillustrated in FIG. 1;

FIG. 3 is an exploded perspective view of the module shown in FIGS. 1and 2;

FIG. 4 is a perspective view of the module shown in FIGS. 1–3 with aheat sink cover removed for clarity;

FIG. 5 is an enlarged and fragmented perspective view of the moduleillustrated in FIG. 4 with other components removed for additionalclarity;

FIG. 6 is a perspective end view of the transceiver module;

FIG. 7 is a perspective bottom view of the transceiver module; and,

FIG. 8 is a plan view on an interior of a heat sink cover member of themodule.

DETAILED DESCRIPTION

FIGS. 1–8 illustrate one preferred embodiment of an optical transceivermodule made according to the principles of the present invention anddesignated by reference numeral 10. As illustrated in FIG. 1, theoptical transceiver module 10 has a first or proximal end portion 12mounted directly on a host circuit card 14 of a known type that iswithin a space 16 formed by a host data transfer system 18, such as amid-range computer system commercially available from InternationalBusiness Machines Corporation. Other types of data transfer orcommunication systems are contemplated for use with the transceivermodule of the present invention, such as input/output devices, or otherperipheral devices. The proximal end portion 12 of the opticaltransceiver module 10 is otherwise attached to the host card by suitableattaching elements, such as screws (not shown). A distal or connectorend portion 20 of the module is releasably coupled to a system wall 22in a manner to be described after being inserted into a system accessopening 24. In this embodiment, the connector end portion 20 isconfigured to be coupled to a suitable push-pull duplex “SC” connector(not shown) in a known manner. While a duplex “SC” type connection isenvisioned, a comparable end portion cooperable with other knownconnectors, such as for example, a single “SC” connector, a “LC”connector, or a “MT-RJ” connector can be used.

Reference is made to FIGS. 2–3, which depict the optical transceivermodule 10 comprising, in essence, a housing assembly 26 including acarrier member 28 mated to a heat dissipating apparatus or heat sinkcover member 30; an optical subassembly 32; an optical retaining unit orassembly 34; and, an electromagnetic interference (EMI) assembly or unit36. Initial reference is made to the carrier member 28 that has,preferably, an integral construction with a rectangular shape and ismade of a suitable material for use in such transceivers. The thicknessof the walls of the carrier member and heat sink cover member areselected to ensure generally uniform heat dissipation yet maintainelectromagnetic interference integrity. Preferably, such a materialserves to dissipate heat and acts as a shield for reducing the emissionsof undesired EMI. Ideally, the carrier member 28 is made of a low cost,die-cast metal, such as aluminum metallized with nickel silver. Also,the carrier member 28 can be made of other appropriate materials thatwill achieve the foregoing functions. Examples of such other carriermaterials include but are not limited to copper, silver and zinc.Besides a nickel silver plating other suitable metals, such as silver orgold can be used for plating the aluminum.

As seen in FIGS. 3–5, the carrier member 28 has an upstanding peripherallip or wall 38 that surrounds and, in part, defines an enclosure 40which is a space between the carrier member 28 and the heat sink covermember 30. The wall 38 fits snugly within a corresponding andcomplementary shaped recess 42 formed in a bottom wall 44 (FIG. 8) ofthe heat sink cover member 30 to maintain EMI integrity. A pair ofspaced apart and generally parallel pedestals 46 and 48 are raised froman enclosure floor surface 50.

Reference is made to the optical subassembly 32 that includes a printedcircuit board member 52 that is sized and configured to be mountedwithin the enclosure on the floor surface 50. The printed circuit boardmay comprise any suitable type of rigid or a flexible type substrate. Aconventional pin connector 51, as seen in FIG. 7, is on the bottom ofthe circuit board member and is registered with a rectangular opening 56formed in the carrier member so as the pin connector can be attached tothe host card in a known manner. The printed circuit board member 52 isformed with a pair of generally parallel and spaced apart cutouts 58 and60. Each of the cutouts 58, 60 receives a respective one of thepedestals 46 and 48; respectively.

An electro-optical transmitter subassembly (TOSA) unit 62 and anelectro-optical receiver subassembly (ROSA) unit 64 are mounted on thepedestals 46 and 48; respectively. Both the TOSA and ROSA units do not,per se, form an aspect of the present invention. Hence, a detaileddescription thereof is not necessary for understanding this invention.However, only those portions necessary for understanding this inventionwill be described. In this embodiment, the TOSA unit 62 includes anelectronic component, such as a laser diode 66 (FIG. 4) that is directlymounted on a silicon optical bench 68 and is wired to an electronicdevice, such as a laser driver chip 70 mounted on the circuit board 52.The laser driver chip 70 tends to operate at temperatures of about 100C. This temperature value is in a range that is significantly higherthan an operational temperature value of the laser diode 66 (e.g., 70 C)which is in a temperature range that is lower than the noted driver chiprange. Without the advantages of this invention, the higher temperaturesof the chip 70 can adversely affect performance of the laser diode; withthe latter operating out of its optimal performance range. The ROSA unit64 includes an optical receiver 72 (FIG. 4) mounted on a silicon opticalbench 74 and is wired to an optical amplifier chip 76 on the printedcircuit board. Both the TOSA and ROSA units are, in turn, wired to aSERDES (serial/deserializer) chip 78; the latter of which also tends tooptimally perform in a temperature range that is higher than that of thelaser diode. The silicon optical benches 68 and 74 are, in turn,correspondingly mounted on and secured to the pedestals 46 and 48;respectively. Preferably, this is accomplished by a layer 75 (FIG. 3) ofa thermally and electrically conductive adhesive material that has beenapplied in a known manner. The material for the layer is a siliconeadhesive grease, such as JM 9000 which is used for bonding electronicparts where high heat transfer is required. This material iscommercially available from General Electric. The thermal adhesive layer75 in this embodiment can have a thickness of about 0.001 inches.Clearly, other thicknesses are contemplated. Whichever materials andthickness are selected they should have thermal conductivities in arange which conducts heat from the laser diode so as to assist inmaintaining the latter at its optimal temperature operating range. Forexample, thermal conductivity can be in a range that is greater than 180watts/mT; wherein m represents meters and T represents temperature inKelvin. In this embodiment, other values of thermal conductivity can beused, such as 200 watts/mT. Accordingly, cooling of the TOSA and ROSAunits is effected by thermal conduction to the carrier member the latterof which is also kept exposed externally to ambient as shown so as toenhance cooling.

It will be further noted that the laser diode 66 and the silicon opticalbench 68 of the TOSA unit 62 by being mounted on the pedestal 46 of thecarrier instead of the printed circuit board is not heated directly fromthe board by the heat generating electronic components, such as theSERDES 78, amplifier 76, and driver 70. Likewise, the components of theROSA unit 64 by being mounted on the pedestal 48 do not have the heat ofsuch components directly affecting them. The foregoing describedconstruction allows a relatively inexpensive yet effective approach forcooling the components, such as the TOSA and ROSA units that should beoperated at lower temperatures than temperatures generated by the chipson the printed circuit board. Also, it will be noted that this coolingis enhanced by reason of the carrier member extending beyond the wall.

Continued reference is made to FIGS. 3–5, wherein a looped optical fiber80 extends from a respective one of the TOSA and ROSA units. Each of theoptical fibers 80 cooperate with a SC optical coupler 82 that opticallycouples the optical fibers to the SC connector. It will be appreciatedthat the optical couplers can be of the SC or LC type. Details of theoptical fibers 80 and their cooperation with the optical couplers 82 donot form a part of the present invention, but are described morecompletely in copending U.S. Ser. No. 09/809,531 entitled: TECHNIQUE ANDAPPARATUS FOR COMPENSATING FOR VARIABLE LENGTHS OF TERMINATED OPTICALFIBERS IN CONFINED SPACES; and, U.S. Ser. No. 09/809,650 entitled: ANOPTICAL FIBER COUPLER AND AN OPTICAL FIBER COUPLER INCORPORATED WITHIN ATRANSCEIVER MODULE.

The heat sink cover member 30 is a heat dissipating apparatus thatessentially functions to transfer heat from the heat generatingelectronics (e.g., Serdes, amplifier and laser driver) as well asshields against electromagnetic interference exceeding undesirablelimits. In this embodiment, the heat sink cover member 30 is a generallythin and rectangularly shaped plate. It can be made of a variety ofmaterials. Preferably they should be the same kind as the carriermember. In this embodiment, the heat sink cover member is made of analuminum coated with nickel silver. A plurality of heat dissipatingelements or fins 84 project from an external surface thereof and aredeployed in the manner illustrated. The fins 84 are generally uniformlyspaced apart relative to each other by a distance of about 5 mm fromcenterline to centerline so as to allow air flow therearound in anydirection and in good cooling convective relationship with each other.Accordingly, this facilitates cooling of the module in a variety of hostsystems that force air therein for cooling in different directions. Inaddition, the noted fin spacing serves to minimize the build up of lintor other similar airborne debris on the module. Further in this regard,the noted spacing between the fins should generally not be less thanabout 2 mm before lint build-up becomes problematic. The fins 84 aretapered from bottom to top for enhancing the amount of surface area thatcan be used for heat dissipation. The present invention contemplatesthat the fins can have other configurations, spacings and heights. Infact, the fins need not substantially cover the upper surface area ofthe heat sink cover. The fins 84 can cover separate and distinctportions of the heat sink cover member, such as only those portionsintended to receive the heat of the chips through conduction. Althoughit is ideal to have the fins made of the same material as the remainderof the cover such need not be the case. In this embodiment, the heatfins 84 terminate in a generally common plane and at a height that ispreferably below the height profile imposed by an end user.

FIG. 8 depicts the bottom wall 44 of the heat sink member having acentrally disposed and integrally formed heat transfer pad 86 having asmooth and flat surface sized to at least cover the chips 70, 76 and 78as well as be in close proximity thereto, for example, in the order ofabout 2 mils to 4 mils. A thermally conductive unit such as a thermaladhesive layer 88 generally uniformly covers the heat transfer pad 86.The thermal adhesive layer 88 mechanically and thermally couples theupper surfaces of the chips to the heat transfer pad 86. In this mannerthere is a greater likelihood that the laser diode 66 will remain at itsdesired operating temperature. Thermal conductivity of the thermaladhesive layer 88, in this embodiment, should be high and can exceedabout 200 watts/mT. Other thermal conductivity ranges are envisioneddepending on the temperatures that are generated by the components. Thethermal layer 88 should be thick enough to accommodate manufacturingtolerance spacings between the pad and the chips. While the adhesivelayer is thermally conductive, it is preferred that it need not beelectrically conductive due to the desire to minimize electromagneticinterference that might otherwise be propagated through an electricallyconductive material. For reliable operation, the thermal adhesive layer88 should be mechanically compliant and due to the relatively flatsurface of the transfer pad 86 the occurrence of bond lines in theadhesive layer 88 is minimized, thus decreasing the tendency of theadhesive to form air gaps therein which would hinder the transfer ofheat. The thermal adhesive layer 88 can be made from a variety ofmaterials including but not limited to silicone adhesives. In thisembodiment, a type 6E3281 silicon adhesive commercially available fromGeneral Electric is used.

In this preferred embodiment, an optical retaining unit 34 comprises apair of plastic optical ferrule coupler retainers 90 for removablyretaining the optical couplers 82 and for being in covering relationshipthereto a retainer cover member 92. Each of the optical ferrule couplerretainers 90 is mounted in a respective pocket 94 formed on the carriermember 28 and removably secures an optical coupler therein. The opticalferrule coupler retainers 90 are secured in place by the retainer covermember 92 that is appropriately secured to the carrier member. Detailsof the optical ferrule coupler retainers 90 do not form an aspect of thepresent invention, but are described in said copending U.S. patentapplication: U.S. Ser. No. 09/809,650. A pair of latches 96 protrudeaxially from one end of the optical ferrule coupler retainers 90 andfacilitate a snap-fit connection with respective ends (not shown) of,for instance, a push-pull, duplex SC connector, whereby the latter areproperly registered to the former for data transmission as is known inthe data transmission field.

Referring back to FIGS. 1, 2, 6 & 7, the retainer cover member 92 isseen to have a unitary construction made of an electrically conductivematerial that primarily serves to shield against EMI, but also serves toconduct heat. The retainer cover member 92 in this embodiment is made ofaluminum coated by nickel silver so as to be suitable for EMI shieldingand heat conduction. Other suitable materials can be used. While aunitary construction is shown, such need not be the case. The retainercover member 92 is secured to the carrier member as by fasteners (notshown) and includes a first set of wall structures 98 that are spacedapart and depend from a central member. These wall structures 98, incombination, with the carrier member 28 and the latches 96 define a pairof lateral electrical connector ports 100 for allowing receipt ofappropriate portions of a push-pull, duplex SC connector.

The retainer cover member 92 also includes a second set of structures102 that, in combination, with the carrier member 28 define respectiveair vents as will be described. In this embodiment, the second set ofstructures 102 includes a pair of laterally extending and generallyU-shaped side arms 106 which cooperate with upstanding wall portions onthe carrier member 28 as illustrated for defining air vents 104 that arelaterally disposed adjacent to the connector ports 100 and extend fromthe plane of the wall. The air vents 104 allow bidirectional passage ofair therethrough, whereby air can easily pass in a generallylongitudinally extending path over a substantial surface portion of themodule. This facilitates greatly the ability of cooler ambient airoutside the data system passing thereinto. Since the external air iscooler, it will also facilitates improved cooling of the module not tomention the internals of the data system. The second set of structures102 includes a plurality of upstanding and spaced apart heat radiatingfins 108 which define air vents 110 that function in a similar manner asthe vents 104. The sizing of the vents can depend on the quantity of airflow therethough. While the present embodiment illustrates a pluralityof discrete vents surrounding a portion of the connector ports, it iswithin the spirit and scope of the present invention to have a singleopening completely surrounding all or part of the connector ports. Whilethe vents are, preferably, positioned over the optical subassembly endof the module which is generally warmer, the vents could be positionedadjacent the proximal end of the module. Moreover, the present inventioncontemplates that the vents can have other configurations. For example,instead of each vent having a rectangular configuration, other geometricconfigurations can be used. The retainer cover member 92 includes a hoodportion 112 that encloses the optical couplers and serves to reduce theEMI as well as enhance heat transfer in this region of the module.

Reference is now made to the electromagnetic interference assembly orunit 36 that releasably retains the distal end of the module in theopening 24 and serves as a shield against EMI emissions. In thisembodiment, the electromagnetic interference assembly or unit 36comprises an integral construction having a generally rectangular frame116 defining a corresponding opening 118 sized to receive slidablytherein one end of the module. A plurality of spaced apart and flexiblyresilient retaining tabs 120 extend from the frame 116 and are bent sothat their distal ends face rearwardly. The tabs 120 are adapted toengage the wall for releasably retaining the module thereto, wherebyportions of the carrier member, the retainer as well as theelectromagnetic interference assembly are external relative to the wallso as to be even better exposed to cooler ambient air. As a result, aneven better heat sink relationship is formed which operates attemperatures lower than those heat sink portions of the module mountedwithin the wall opening. The electromagnetic interference assembly iscoupled to at least peripheral portions of the second set of structuresand at least peripheral portions of the first end portion of the carriermember for releasably coupling the optical transceiver to the wallopening.

A screen assembly 122 is integrally coupled to the frame 116 in aflexibly resilient manner and is biased in a given angular orientationto the frame for shielding the wall opening, an end of the transceiver,and the vents. The screen assembly 122 includes a plurality of generallycircular openings or vents 124 that are sized and spaced for controllingelectromagnetic interference emissions and for allowing air flow to thevents 104 and 110 to allow the passage of air over the surface of themodule. When the electromagnetic interference unit 36 is slid over themodule the screen assembly 122 bends slightly due to inherent biasingthereof relative to the retainer member 92 to place its openings orvents 124 at an oblique angular orientation, such as shown, relative toa vertical plane containing the vents 104 and 110. The obliqueorientation of the screen assembly 122 facilitates a presentation of agreater number of the vents 124 in the path of the air passing throughthe vents 104 and 110; in comparison to the number of vents presented ifthey are generally parallel to a vertical plane including the vents 104and 110. The size of each vent 124 is such as to not only facilitate airflow, but also limit EMI emissions. In this embodiment, the each of thevents 124 has a diameter size of about 2 mm to about 3 mm. Other sizesare contemplated, such as 3 mm to about 6 mm. The screen assembly 122does not have an opening over the portion thereof that is in overlyingrelationship to the hood portion 112. The screen assembly 122 haslateral flaps 126 that are joined to the sides of the carrier member 28.The electromagnetic interference unit 36 is, preferably, an integralpiece that is made of aluminum plated with a nickel silver as are theother components of the module for heat dissipation and EMI reasons.While a screen assembly is shown, EMI blocking can be accomplished witha solid member covering the vents 104 and 110. Also, the screen need notbe at an oblique angle but can be placed parallel to a vertical planecontaining the vents 104 and 110. While the retainer and the screen unitare two pieces, the present invention contemplates that they can be oneunit.

Accordingly, there is provided a method of cooling an opticaltransceiver that is mountable to an opening in a wall. The methodcomprises the steps of: providing an optical transceiver having at leastone end portion that is insertable within the wall opening; and,ventilating ambient air over a major portion of the transceiver bymounting the one end portion to a wall so that at least one vent isformed within confines of the wall opening which allows air to passtherethrough and over the transceiver. Ventilating can be achievedpassively or with the use of circulating devices (not shown) within thedata transfer system.

The embodiments and examples set forth herein were presented to bestexplain the present invention and its practical application and tothereby enable those skilled in the art to make and use the invention.However, those skilled in the art will recognize that the foregoingdescription and examples have been presented for the purposes ofillustration and example only. The description set forth is not intendedto be exhaustive or to limit the invention to the precise formsdisclosed. Many modifications and variations are possible in light ofthe above teachings without departing from the spirit and scope of theappended claims.

1. An optical transceiver comprising: a housing assembly including acarrier member and a heat sink cover member coupled to a portion of saidcarrier member to define at least a portion of an enclosure therewith;an optical subassembly including an electro-optical transmitter unitpositioned within said enclosure; a retainer assembly mounted on a firstend portion of said carrier member and enclosing portions of saidoptical subassembly; said retainer assembly including a first set ofstructures which, in combination, with said carrier member define atleast one electrical connector port for allowing connection of anelectrical connector to said optical subassembly; said retainer assemblyincluding a second set of structures which, in combination, with saidcarrier member define at least one vent surrounding portions of saidconnector port, said vent allows bidirectional passage of airtherethrough, whereby air can easily pass generally over a substantialsurface portion of said housing assembly; and, an electromagneticinterference assembly connected to at least peripheral portions of saidsecond set of structures and at least peripheral portions of said firstend portion for releasably coupling said optical transceiver to anopening of a wall.
 2. The optical transceiver of claim 1 wherein saidelectromagnetic interference assembly includes a frame having aplurality of spaced apart and flexibly resilient retaining tabsextending therefrom, said tabs allowing said optical transceiver to beinserted into a wall opening and releasably retained thereby with a walldefining the wall opening, said electromagnetic interference assembly ismade of an electrically conductive material which reduceselectromagnetic interference emissions of said optical transceiver. 3.The optical transceiver of claim 2 further including a screen assemblycoupled to said optical transceiver so as to be positioned adjacent toand covering at least a portion of said vent, said screen assembly beingmade of a material that reduces electromagnetic interference and iscoupled to said frame and is adapted to be positioned adjacent to andcovering at least a portion of said vent defined by the opticaltransceiver and the wall, said screen assembly having a plurality ofscreen openings for allowing passage of air therethrough and reducingemission of electromagnetic interference.
 4. The optical transceiver ofclaim 3 wherein said screen openings are sized and spaced forcontrolling electromagnetic interference emissions and for allowing airflow to said vent.
 5. The optical transceiver of claim 3 wherein saidscreen assembly is integrally coupled to said frame in a flexiblyresilient manner and is biased in a given angular orientation thereto sothat said screen assembly presents relatively more of said openings tosaid vent than would otherwise be presented if said openings were in aplane parallel to said vent.
 6. The optical transceiver of claim 1further including a plurality of heat dissipating elements extendingfrom said heat sink cover member, said heat dissipating elements beingspaced apart from each other by a sufficient distance so as to minimizetrapping of airborne debris thereby.
 7. The optical transceiver of claim1 wherein said second set of structures include a pair of laterallyextending arms which cooperate with said carrier member to define acorresponding pair of lateral vents positioned adjacent said connectorport and at least an upper vent above said connector port between saidlateral vents.
 8. The optical transceiver of claim 1 wherein saidelectro-optical transmitter unit includes a first electronic devicewhich operates at a first temperature range and a second electronicdevice which operates at a second temperature range that is differentfrom said first range; said first electronic device being thermallycoupled to an internal surface of said carrier member so as to transferheat thereof by conduction to said carrier member, and said secondelectronic device being mounted on a substrate located within saidenclosure which substrate is not in direct thermal contact with saidcarrier member; and, a thermally conductive unit coupling said secondelectronic device to an internal wall of said heat sink cover member ina manner so as to transfer heat by conduction from said secondelectronic device to said heat sink cover member and away from saidfirst electronic device.
 9. A data transfer system including a wallhaving an access opening and an adapter card assembly, in combinationwith an optical transceiver which is mounted to said wall accessopening, said optical transceiver comprising: a housing assemblyincluding a carrier member and a heat sink cover member coupled to aportion of said carrier member to define at least a portion of anenclosure therewith; an optical subassembly including an electro-opticaltransmitter unit positioned within said enclosure; a retainer assemblymounted on a first end portion of said carrier member and enclosingportions of said optical subassembly; said retainer assembly including afirst set of structures which, in combination, with said carrier memberdefine at least one electrical connector port for allowing connection ofan electrical connector to said optical subassembly; said retainerassembly including a second set of structures which, in combination,with said carrier member define at least one vent surrounding portionsof said connector port, said vent allows bidirectional passage of airtherethrough, whereby air can easily pass generally over a substantialsurface portion of said housing assembly, and, a electromagneticinterference assembly connected to at least peripheral portions of saidsecond set of structures and at least peripheral portions of said firstend portion for releasably coupling said optical transceiver to theaccess opening.
 10. The system of claim 9 wherein said electromagneticinterference assembly includes a frame having a plurality of spacedapart and flexibly resilient retaining tabs extending therefrom, saidtabs allowing said optical transceiver to be inserted into the accessopening and releasably retained thereby with the wall, saidelectromagnetic interference assembly is made of an electricallyconductive material which reduces electromagnetic interference emissionsof said optical transceiver.
 11. The system of claim 10 furtherincluding an electrically conductive screen assembly coupled to saidframe positioned adjacent to and cover at least a portion of said vent.12. The system of claim 9 further including a plurality of heatdissipating elements extending from said heat sink cover member, saidheat sink dissipating elements being spaced apart from each other by asufficient distance so as to minimize trapping of airborne debristhereby.
 13. An optical transceiver comprising: a housing assemblyincluding a carrier member and a heat sink cover member joined togetherto define a portion of an enclosure therebetween; an optical subassemblywithin said enclosure, said optical subassembly comprising anelectro-optical transmitter unit including a first electronic devicewhich operates at a first temperature range and a second electronicdevice which operates at a second temperature range that is higher thanthe first temperature range; said first electronic device beingthermally coupled to an internal surface of said carrier member so as totransfer heat thereof by conduction to said carrier member, and saidsecond electronic device being mounted on a substrate located withinsaid enclosure which substrate is not in direct thermal contact withsaid carrier member; and, a thermally conductive unit coupling saidsecond electronic device to an internal wall of said heat sink covermember in a manner so as to transfer heat by conduction from said secondelectronic device to said heat sink cover member and away from saidfirst electronic device, whereby the first electronic device ismaintained cooler than the second electronic device.
 14. The opticaltransceiver of claim 13 further comprising: a retainer assembly mountedon a first end portion of said carrier member and enclosing portions ofsaid optical subassembly; said retainer assembly including a first setof structures which, in combination, with said carrier member define atleast one electrical connector port for allowing connection of anelectrical connector to said optical subassembly; said retainer assemblyincluding a second set of structures which, in combination, with saidcarrier member define at least one vent surrounding portions of saidconnector port, said vent allows bidirectional passage of airtherethrough, whereby air can easily pass generally over a substantialsurface portion of said housing assembly; and, an electromagneticinterference assembly connected to at least peripheral portions of saidsecond set of structures and at least peripheral portions of said firstend portion for releasably coupling said optical transceiver to anopening of a wall.
 15. The optical transceiver of claim 14 wherein saidthermally conductive unit comprises a thermally conductive adhesivematerial which has reduced electrical conductivity properties forinhibiting the transfer of electromagnetic interference.
 16. The opticaltransceiver of claim 14 wherein said electromagnetic interferenceassembly is made of an electrically conductive material which reduceselectromagnetic interference emissions of said optical transceiver andincludes a frame having a plurality of spaced apart and flexiblyresilient retaining tabs extending therefrom, said tabs allowing saidoptical transceiver to be inserted into a wall opening and releasablyretained thereby with a wall defining the wall opening.
 17. The opticaltransceiver of claim 14 further including an electrically conductivescreen assembly coupled to said optical transceiver positioned adjacentto and covering at least a portion of said vent.
 18. An opticaltransceiver comprising: a housing assembly including a carrier memberand a heat sink cover member joined together to define a portion of anenclosure therebetween; an optical subassembly within said enclosure,said optical subassembly comprising an electro-optical transmitter unitincluding a laser diode which operates at a first temperature range anda laser driver which operates at a second temperature range that isdifferent from said first range; said laser diode being thermallycoupled to an internal surface of said carrier member so as to transferheat thereof by conduction to said carrier member, and said laser driverbeing mounted on a substrate located within said enclosure whichsubstrate is not in direct thermal contact with said carrier member;and, a thermally conductive unit coupling said laser driver to aninternal wall of said heat sink cover member in a manner so as totransfer heat by conduction from said laser driver to said heat sinkcover member and away from said laser diode, whereby the laser diode ismaintained cooler than the laser driver.
 19. An electromagneticinterference apparatus for use in combination with an opticaltransceiver having a housing assembly including an end portion with avent which allows air to flow therethrough, said electromagneticinterference apparatus is made of a material which reduceselectromagnetic interference emissions, said electromagneticinterference apparatus comprising: a frame; a plurality of spaced apartand flexibly resilient retaining tabs extending from said frame, saidtabs allowing the optical transceiver to be inserted into a wall openingfor releasably retaining the optical transceiver within the wallopening; and, a screen assembly coupled to said frame so as to bepositioned adjacent to and covering at least a portion of the vent, saidscreen assembly including a plurality of screen openings which allowpassage of air therethrough and reduce emissions of electromagneticinterference.
 20. The apparatus of claim 19 wherein said screen assemblyis angularly oriented relative to a generally longitudinal flow path ofair through the vent so as to increase the number of said screenopenings which can pass air therethrough relative to a number of saidscreen openings which could pass air if said screen openings weregenerally parallel to a vertical plane of said vent.